Mark Zartler prepares a tiny amount of marijuana for a vapor treatment for his autistic daughter, Kara, who hits herself in the face. He says she stops hurting herself minutes after inhaling the vapor.

Kara Zartler, 17, has cerebral palsy and is autistic. She just got home from school, and she’s in the kitchen with Mom, dad, her daily caregiver and the family’s dogs.

Her mom talks with Kara.

“Kara, can you look? He wants to take your picture. Can you keep looking? Over here,” says Christy Zartler, who’s a pediatric nurse practitioner.

She says her daughter, who’s non-verbal, is having a good day.

“Look,” Zartler says. “She smiled at you. That’s so positive.”

It’s not always this way, says her father, Mark Zartler, a software engineer.

“She has self-injurious behaviors,” he says. “These have been a constant in her life since she was 4. She will hit herself repeatedly in the face and gets into a cycle and just can’t stop. That just goes on and on.”

Zartler’s behavior was captured in a home video and posted on Facebook and YouTube last month.

Warning: Video might be difficult to watch for some viewers.

The video shows Kara screaming as she’s strapped in a car seat. Then she’s in a living room rocking chair, rhythmically hitting herself with both fists on each side of her head.

Doctors say it’s how she responds to pain, likely from cerebral palsy.

It’s hard to know. It’s also hard to watch.

In the video, Mark Zartler puts a mask to Kara’s face and squeezes cannabis vapor from a plastic bag he’s filled. About three minutes later, Kara is calmer. She still rocks and grunts. But the episode is over, her mom says.

“It’s lessened. It doesn’t completely stop it,” Christy Zartler says. “But it slows her down. It slows her mind and her brain down to where she’s just more focused and aware.”